Rebase fix for long running simulations on current brian2

[jangmarker]

Probably best course of action:

• fork brian2 in this organization
• apply the patch to current master [WIP] Use an epsilon independent of dt when comparing times brian-team/brian2#1057
• install brian2 from that repository (using pip install <git url>)

[jangmarker]

done, see f141c7a and https://github.com/excinhbal/brian2/tree/2.3.0.2_excinhbal_fixes